While this consideration is not publicly acknowledged — the Washington Post notes that Gates wanted to shake things up and select “someone who would help the Marine Corps chart a course beyond the current wars“” — his more supportive stance towards ending the DADT likely weighed on the decision:
Sources have informed LezGetReal that General Amos’ position on the repeal of Don’t Ask, Don’t Tell mirrors that of Admiral Michael Mullen, the current Chairman of the Joint Chiefs of Staff. This means that General Amos believes that the study should be finished before the law is repealed, and the best way to move forward on repeal can be determined. General Amos is said to be more open to change than General Conway has been, or either General Dunford or General James Mattis, who were also considered for this job. Additionally, Generals Dunford and Mattis are said to be far less willing to consider a repeal of DADT and far closer to General Conway’s views on the issue of lesbians and gays serving openly.
If Amos is willing to think not only beyond current wars but also conservative social norms — which is where Conway clearly fell short — then his nomination sounds like a good thing for the institution as a whole and particularly its closeted gay members. The success of repeal will depend heavily on how the military implements regulations overturning the ban and Amos probably be willing to explore more inclusive changes than his immediate predecessor.
The other point worth reiterating is that one’s opposition to repealing DADT has more to do with general attitudes about social policy than any kind of concerns about the future of the military. After all, if Gates is willing to nominate someone he hopes will shake up the Marine Corps and secure its future, his selection of Amos — if we are too believe the rumors about his more liberal DAD views — suggests that that is very much compatible with open service.